386 Lake Wakatipu, New Zealand. (July, 
as having a common origin, and being but portions of the same 
valley, the upper part of which is filled with fourteen hundred 
feet of water, and the lower portion by an unknown depth of 
worn and rounded shingle. The rocks in which the valley is 
formed are, for the most part, clay slates and gold-bearing mica 
schists, which are very much curved and twisted, and in many 
places green with chlorite. 
When we look for the causes, the working power that has pro- 
duced these grand results, the mind becomes awestruck by the 
magnitude of the forces which have formed not only the grand 
valley, but the very mountains in which it exists. 
What pictures pass before us when we follow in rapid review 
the great changes that have resulted in the formation of these 
rugged mountains, gray and scored as they are by time. We see 
the sediments which for ages have slowly accumulated at the 
bottom of the sea, and formed the mud and ooze of ancient 
oceans, by the action of heat and great pressure hardenéd and 
crystallized into rock, and then slowly upheaved by the mysteri- 
ous volcanic forces into lofty mountain chains whose snowy peaks . 
gleam above the clouds, only to be slowly removed, to have great 
valleys opened in their sides, and their most solid rocks wom 
away and carried down particle by particle to be spread out 
once more at the bottom of the sea. If we consider these changes, 
grand as they are, as but a single circle in the great cycle of 
geological time, we can appreciate to some extent the wonders 
of the history that is written on the rocks. Itis only to the last 
chapter in this history — the formation of the valley — that we 
would ask your attention. . 
Valleys may be considered as owing their origin, primarily, to 
one of three causes: (1.) They are formed by a folding of the 
rocks, thus forming depressions, the sides of which slope inwards 
towards the axis, hence designated as synclinal valleys. Er 
amples of valleys formed in this way are to be met with wherever 
stratified rocks have been upheaved, as in the Sierra Nevada, 
Rocky, and Alleghany Mountains. (2.) Valleys are sometimes 
formed by the fracturing of the earth’s crust by volcanic forces. 
Valleys of this kind are seldom seen, being confined to regions 
of great volcanic disturbance. (3.) The kinds of valleys above 
noticed are usually greatly modified by denudation, which 18 80- 
other great agent in their formation. By denudation we under- 
stand the wearing away of rocks not only by wind 
rain, but also by the more powerful action of ice and running 
water, the operation of which we can see every where about us. 
